Oral infection represents an important route of human cytomegalovirus (HCMV) transmission. HCMV infection is also among the most common causes of oral diseases associated with AIDS patients. Understanding the mechanism of HCMV infection in oral mucosa as well as other parts of the oral cavity will provide insight into developing new drugs and novel strategies for treatment and prevention of HCMV-associated oral diseases. The objective of the proposed research is to study HCMV chromatin modifications and their roles in viral infection in oral mucosa. Recent studies in our laboratory have shown that epigenomic modifications, including histone tail changes by methylation, have been found in HCMV chromatin in human primary oral cell and tissue cultures. Furthermore, preliminary studies have suggested that specific viral proteins affect the epigenetic modifications of viral chromatin, and that some of these modifications specifically modulate the expression of viral gene expression required for HCMV productive infection. In the initial part of the proposed study, we will screen a collection of HCMV mutants with deletion of a single viral open reading frame (ORF) to isolate mutants that exhibit altered viral chromatin modifications and to identify viral determinants important for specific modifications of HCMV chromatin in oral mucosa. Experiments will then be carried out to study the roles of the identified modifications of viral chromatin in regulating viral gene transcription and supporting viral infection in oral cells. Furthermore, experiments will also be carried out to investigate how the viral determinants modulate specific HCMV chromatin modifications by interacting with the epigenetic remodeling complexes in order to facilitate HCMV infection in oral cavity. These studies will lead to the identification of viral determinants important for HCMV chromatin modifications and for viral infection in oral mucosa. Furthermore, our studies will investigate how HCMV replicates in oral mucosa and how HCMV-encoded determinants function to modulate HCMV chromatin modifications and support viral infection in oral mucosa. Our results will provide insight into the mechanism of HCMV infection in oral mucosa and facilitate the development of novel strategies for treatment and prevention of the transmission as well as infection of HCMV in oral cavity.